A new method is described for fabricating autonomic, self-healing, deformable organogels. We combined imidazolium-based poly(ionic liquid) (PIL) and azobenzene-grafted poly(carboxylic acid) (PAA-Azo) in N,N-dimethyl formamide. Further, complexing PIL with unirradiated (trans) or irradiated (cis) PAA-Azo tuned the elastic modulus of the organogel.
Numerous catechol-containing polymers, including biodegradable polymers, are currently heavily discussed for modern biomaterials. However, there is no report combining poly(phosphoester)s (PPEs) with catechols. Adhesive PPEs have been prepared via acyclic diene metathesis polymerization. A novel acetal-protected catechol phosphate monomer was homo- and copolymerized with phosphoester comonomers with molecular weights up to 42000 g/mol. Quantitative release of the catechols was achieved by careful hydrolysis of the acetal groups without backbone degradation. Degradation of the PPEs under basic conditions revealed complete and statistical degradation of the phosphotri- to phosphodiesters. In addition, a phosphodiester monomer with an adhesive P-OH group and no protective group chemistry was used to compare the binding to metal oxides with the multicatechol-PPEs. All PPEs can stabilize magnetite particles (NPs) in polar solvents, for example, methanol, due to the binding of the phosphoester groups in the backbone to the particles. ITC measurements reveal that multicatechol PPEs exhibit a higher binding affinity to magnetite NPs compared to PPEs bearing phosphodi- or phosphotriesters as repeating units. In addition, the catechol-containing PPEs were used to generate organo- and hydrogels by oxidative cross-linking, due to cohesive properties of catechol groups. This unique combination of two natural adhesive motives, catechols and phosphates, will allow the design of novel future gels for tissue engineering applications or novel degradable adhesives.
Significance: Reported is a palladium-catalyzed direct arylation of heteroarenes (benzoxazole, oxazole, caffeine, 1,2,3-triazole) with aryl tosylates.The first examples of direct arylation using mesylates as arylating reagents are also described. This cross-coupling involves the use of Pd(OAc) 2 /XPhos as a catalytic system and K 2 CO 3 as a base. In the case of benzoxazole, the addition of a catalytic amount of t-BuCO 2 H improves the coupling. The scope of the reaction has been studied with electron-rich and electron-poor aryl tosylates and mesylates to give products in 58-99% yields. Single examples of an ortho-substituted aryl tosylate and an alkenyl tosylate were also described.Comment: Direct arylation of aromatic and heterocyclic compounds has attracted significant attention mainly as a more efficient and atom economic method which is complementary to the classical cross-coupling processes using metalorganic partners (I. J. S. Fairlamb Chem. Soc. Rev. 2007, 36, 1036. The use of tosylate and mesylate electrophiles compared to halides and triflates provides a further economic factor. The extension of this C-H activation methodology to other heteroaromatics and the broader use of aryl mesylates are anticipated.
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